As insect pests move in: Mid-South cotton awaits rain

It's been “one of those years” in Mid-South cotton, a little out-of-whack to say the least. The weather has been abnormally dry and many fields have been infested with thrips, plant bugs and spider mites.

One Mid-South state that has perhaps the most promising cotton crop of all simply didn't plant much of it. According to USDA, Louisiana cotton acres dropped from 635,000 acres in 2006 to 380,000 acres in 2007, a figure expected to fall even further by harvest.

Many cotton producers increased their acreage of corn this season, not a surprise given the excellent corn prices. But in the north Delta, an Easter freeze killed much of the corn that had emerged. Some who replanted to cotton are today scratching their heads at a new weed — Roundup Ready corn.

According to Louisiana Extension cotton specialist Sandy Stewart, final cotton acreage in the state will probably come in around 300,000 acres, 80,000 acres less than USDA's March estimate and significantly below previous years' plantings.

The crop is faring well, he says. “We've been fortunate. Overall, it's hard to find a lot to complain about. We've had the occasional thrips, aphids and spider mite issues. I would have liked to have seen a little more sunlight, but in general we're okay.”

Over the next month, the cotton crop will grow rapidly, noted Stewart, as days in the mid-90s and hotter will be more frequent. “In a lot of places, we're getting close to layby and I know some plant growth regulators have gone out. With the amount of corn we have and the number of fields where cotton is adjacent to corn, we're going to have to watch plant bugs very closely.”

Tennessee

Two weeds are causing problems in west Tennessee cotton fields, according to University of Tennessee weed scientist Larry Steckel — giant ragweed and Roundup Ready corn.

Roundup Ready corn is showing up in fields where the crop was killed by an Easter freeze. Well, most of it was killed. Some growers who chose to replant to cotton instead of going back to corn have been surprised to see surviving corn plants in cotton fields.

This situation “is fairly common in the cotton counties where we went back to cotton,” Steckel said. “Most people, including me, thought we could get by with 4 ounces of Select Max (to take out the corn), but it got so dry that it didn't really take. As a result, we have a lot of Roundup Ready corn in our Roundup Ready cotton in places.”

The answer is to go with the highest rates of a graminicide, whether it's Select Max, Fusilade, Poast, Arrow, or other, Steckel said.

“Corn has had a head start and as a weed, it's going to be competitive. And as dry as we've been this spring, weeds really magnify drought stress. The corn is going to have a better advantage getting the water than the cotton.”

Steckel also reports that giant ragweed is starting to move from field borders into the cotton crop. “Glyphosate on a good day is going to give you 60 percent control. There have been some discussions on whether we have a resistance, but in my experience, glyphosate has never been very good on it. But we're really seeing it become an issue.”

Steckel noted that the biotype of giant ragweed appearing in cotton fields appears to be different from the biotype found in non-crop areas. Seeds gathered from giant ragweed found around railroad tracks were found to germinate in one flush in March, while those found in and around a soybean field germinated from March through June. “We're getting a population that is adapting by germinating later.”

Steckel is trying several combinations of herbicides on the weed — which can grow to 12 feet — including Staple and Envoke. “I have some hope that we can at least make it a less competitive weed.”

Mississippi

According to Extension entomologist Angus Catchot, the state's cotton crop “had a really good start, then we had a seven- to 10-day period of cool conditions, which slowed the crop. Then we had some of the heaviest thrips pressure we've had in a long time in some areas of the state.

“A lot of the cotton doesn't look as good as it should because of that, but over the last five to seven days (the first week of June) we have had better conditions, and the crop has started growing off. Cotton looks a lot better, but right now, we need rain in a lot of areas. That's our biggest concern. The east side of the state is drought-stressed.

“Overall, I rate the crop at average to slightly above average, but it will go down quickly if we don't get some water.”

Arkansas

A little rain “would solve a lot of problems,” said Tom Barber, Arkansas Extension cotton specialist. “We have cotton from four-leaf all the way up to squaring. Farmers are starting to water.”

The state has also suffered through thrips infestations, as well as spider mite infestations at a few locations.

According to Gus Lorenz, Arkansas Extension entomologist, the thrips infestation “was one of the heaviest we've seen in recent years. We're just about to get them beat down now. Our big problems now are spider mites, particularly in the northeast part of the state.”

The spider mite problems have been tied to growers not burning down weeds in the field prior to planting. “A lot of times, they just rehip. Where they had henbit in the field is where they've had severe mite infestations.”

Lorenz noted that cotton in the south part of the state “is a little ahead of the cotton in the northeast and it's beginning to square. Our plant bug levels for this time of the year are above normal, and some treatments are going out. It's not unmanageable, but it's certainly not good to see these levels of plant bugs this early in the season.”

Much of the plant bug infestations could be attributed to increased acreage of corn, according to Lorenz. “We expect to see more plant bugs and later on, bollworms coming out of corn.”

Missouri

Dunklin County Extension agent Mike Milam says dry weather persists in the Bootheel, “and we're about a week away from things getting worse. But right now, we have some cotton squaring and things are looking pretty good overall. I've seen a lot of producers turning on their center pivots. It's been that kind of a year. We've missed so many rains.”

Milam says thrips pressure has been lighter in the Bootheel than usual. “The biggest problem we have now is that there are a lot of insects out there. A few people have sprayed for spider mites. Bollworms and budworms are both building.”

The good news so far is that only 57 boll weevils have been caught in the state's trapping program this season, across over 400,000 acres.